Field
Embodiments of the present invention relate to fluid-filled lenses and in particular to variable fluid-filled lenses.
Background
Basic fluid lenses have been known since about 1958, as described in U.S. Pat. No. 2,836,101, incorporated herein by reference in its entirety. More recent examples may be found in “Dynamically Reconfigurable Fluid Core Fluid Cladding Lens in a Microfluidic Channel” by Tang et al., Lab Chip, 2008, vol. 8, p. 395, and in WIPO publication WO2008/063442, each of which is incorporated herein by reference in its entirety. These applications of fluid lenses are directed towards photonics, digital phone and camera technology and microelectronics.
Fluid lenses have also been proposed for ophthalmic applications (see, e.g., U.S. Pat. No. 7,085,065, which is incorporated herein by reference in its entirety). In all cases, the advantages of fluid lenses, such as a wide dynamic range, ability to provide adaptive correction, robustness, and low cost have to be balanced against limitations in aperture size, possibility of leakage, and consistency in performance. Endoscopes are optical tools which allow users to view areas where typical line-of-sight viewing is not feasible, such as areas within the body. An endoscope can be rigid, referred to more commonly as a borescope, or flexible, referred to usually as a fiberscope. Endoscopes typically contain a series of lenses along an optical path to provide an image of an object at one end of the endoscope to a user viewing through the other end of the endoscope. The use of conventional lenses within endoscopes defines a specific working distance at which the object being viewed is in focus. Deviating away from this working distance will cause the object to appear blurry to the user viewing it at the opposite end. Thus, the endoscope must be kept stationary at a certain distance away from an object in order to maintain clear focus of the object. Changing the working distance, or focal length, can be achieved by switching between lenses of various optical powers within the endoscope. However, once the endoscope is in use, it is very difficult to change any of the lenses used within it. Furthermore, only discrete working distances and magnification powers may be set using stationary lenses with rigid shapes.